low latency USB audio broken? [was Re: [linux-audio-user] open source firewire]

Ryan Gallagher ruinaudio at comcast.net
Sun Nov 28 20:08:13 EST 2004


On Sun, 2004-11-28 at 19:11 -0500, Lee Revell wrote:
> On Sun, 2004-11-28 at 17:49 -0600, Ryan Gallagher wrote:
> > Yeah, I know how to do playback only (thanks - see the tests for results
> > of -P).  The emi 2|6 has no mic pres and I don't have a line level
> > source to feed it atm so I can't do capture only tests... as of now I
> > havent gotten it to actually capture anything, that'll be the next round
> > of testing.
> > 
> > I'm also playing around with -n with some preliminarily good results...
> > I'll post a followup in a while.
> 
> Sorry, I missed that.
> 
> Anyway this discussion should move to the JACK list.

Ok,

Some people here may be interested in seeing where I'm at though so
here's the tail end of what I'm posting to jackit-devel:

Guessing that -> alsaplayer -r -d hw:1 -f 64 -g 4 
is analogous to -> jackd -R -d alsa -d hw:1 -p 64 -n 4 -P

I tried jackd -R -d alsa -d hw:1 -p 64 -n 8 and YEAH!!! low latency
duplex!  Err... almost...

So I decided to get input working (emi has no mic pres so I hooked up a
tape deck and played some "Schoolhouse Rock" through the emi.

Things sound good for a while then I get a blast of about 22 messages
like these (accompanied by some ugly noise in playback):

	delay of 1771.000 usecs exceeds estimated spare time of 1291.000; restart ...
	18:35:06.777 XRUN callback (1).
	delay of 8947.000 usecs exceeds estimated spare time of 1291.000; restart ...
	18:35:06.788 XRUN callback (2).
	delay of 4257.000 usecs exceeds estimated spare time of 1303.000; restart ...
	18:35:06.984 XRUN callback (3).
	delay of 8909.000 usecs exceeds estimated spare time of 1303.000; restart ...
	18:35:06.993 XRUN callback (4).

Then nice clean playback again for a few minutes and another blast:

	delay of 5536.000 usecs exceeds estimated spare time of 1234.000; restart ...
	18:45:06.692 XRUN callback (23).
	delay of 9070.000 usecs exceeds estimated spare time of 1234.000; restart ...
	18:45:06.702 XRUN callback (24).
	delay of 5056.000 usecs exceeds estimated spare time of 1234.000; restart ...
	18:45:06.897 XRUN callback (25).
	delay of 8971.000 usecs exceeds estimated spare time of 1234.000; restart ...
	18:45:06.907 XRUN callback (26).
	delay of 4544.000 usecs exceeds estimated spare time of 1229.000; restart ...
	18:45:07.101 XRUN callback (27).

Rinse and repeat.

Anyway, the upshot is I'm excited to be getting this close to having my
emi 2|6 be functional low-lat and full duplex.

I'll continue the hunt on jack.

-ry

-- 
Ryan Gallagher <ruinaudio at comcast.net>




More information about the Linux-audio-user mailing list